1. Field of the Invention
The present invention relates to a device for connecting a belt of a height adjustable furniture piece and, in particular, it relates to a device for connecting a belt of a height adjustable furniture piece to a spring element for supporting a lifting operation of the movable part of the furniture piece against the force of gravity.
2. Discussion of the Related Art
From prior art, there is known a furniture piece with a device for a movement synchronization of supporting elements. FIG. 1 shows an example for a known furniture piece according to EP 1 987 734 A1 with a device for movement synchronization of supporting elements. In particular, EP 1 987 734 A1 discloses a device including two support elements 1,2, each support element comprising a first extension member 4 and a second extension member 5, wherein the first extension member 4 and the second extension member 5 are arranged displaceable with respect to each other in a telescopically manner. Furthermore, the device includes at least a first belt 6 with one end of which being fixed to the first extension member 4 of the first support element 1 and the other end of which being fixed at the first extension member 4 of the second support element 2. A deflection of the first belt 6 by means of pulleys 8,9,10 is carried out in a manner, such that a relative displacement between the first extension member 4 and the second extension member 5 of the first support element 1 results in a synchronous displacement between the first extension member 4 and the second extension member 5 of the second support element 2, relative to each other. Furthermore, the belt 6 is a steel belt and each of the pulleys 8, 9, 10, 11, 12, 13 are supported by only one ball bearing and the admissible tilt of the ball bearing supports centering the steel belt 6, 7.
Furthermore, there is known a furniture piece with a device for movement synchronization of supporting elements as shown in FIG. 2. In comparison with the prior art mentioned above, the device shown in FIG. 2 discloses a spring element 30 connected to a belt 6 to assist lifting of the movable part of the furniture piece against force of gravity.
The disadvantage of the connection between the spring element 30 and the belt 6 as shown in FIG. 2 is subsequently explained:
As shown in FIG. 2, a rope 40 is provided between the spring element 30 and the belt 6. If the movable part of the furniture piece is lifted, due to the kinematical interaction of the belt 6 and the pulleys 8, 9, 10, 11, 12, 13, the rope 40 which connects the spring element 30 and the belt 6 is moved. Thereby, the point of connection connecting the rope 60 and the belt 6 is moved with the belt 6 as well. Thereby, the spring element 30 is tensioned and the spring force acts against the force of gravity of the movable part of the furniture piece. Because of the pulley block (interaction of belt 6 and pulleys 8, 9, 10, 11, 12, 13), the moving distance of the point connecting the rope 40 and the belt 6 is twice as large as the moving distance of the movable part of the furniture piece while moving up or down. Therefore, the rope 40 needs a sufficient dimension in length. Furthermore, there is a problem since the spring rate of the spring element 30 is not constant and changes as a function of the height of the movable part of the furniture piece. Furthermore, the possible elongation of the spring element 30 has to be sufficient for covering the entire height change of the movable part of the furniture piece. Furthermore, as a further disadvantage since the belts 6 are heavy and expensive, the belts 6 are quite long in such a construction as shown in FIG. 2.